The subject matter disclosed herein relates to a solder paste transfer process and, more particularly, to a solder paste transfer process for non-planar surface mount assemblies.
Standard circuit cards are flat and do not have heat sinks, components or connectors attached to them. This allows solder paste to be applied using an automated screen print process. When a circuit card is not flat, however, the automated process cannot be used and the standard alternate process is to dispense solder paste onto the circuit card locations. This process is often very time consuming and has a high potential for causing solder defects.
Dispensing improvement efforts have included the introduction of the auger positive displacement valve. Auger valves use rotating threads in close proximity to a cylinder wall to force paste downward through a needle tip. These valves rely on fluid pressure to supply a continuous feed of paste into the auger chamber during dispense. Although this can be more precise than time/pressure valves, auger valves usually are more complicated to operate and have a larger degree of variables controlling dispense volume. Dispensing solder paste is also a very labor dependant process increasing assembly cost.